Chromosome Number Of Plants Research Articles

ПОЛИПЛОИДИЯ У ВОДНЫХ И ПРИБРЕЖНО-ВОДНЫХ СОСУДИСТЫХ РАСТЕНИЙ СЕВЕРО-ВОСТОКА АЗИИ

The chromosome numbers of aquatic and semiaquatic vascular plants growing in extreme North-East Asia, east of the Lena River, were analyzed. We have reviewed the information about the karyological peculiarity of the aquatic flora based on published data, including our own definitions. The karyological data are considered depending on the taxonomic position, distribution and ecological characteristics of the species. The chromosome numbers are known for 119 out of 123 species. There is no data on Zannichellia komarovii, Eleocharis termale, Stuckenia subretusa and Potamogeton sibiricus. In the aquatic flora of North-East Asia, the proportion of polyploids is higher (79%) than that reported for the entire Beringian flora (69%). We analyzed species for the presence of polyploidy depending on the type of area. Analysis by latitudinal groups revealed that all Arctic and hypoarctic species of aquatic plants are polyploids. The minimum proportion of polyploids is observed among arctoboreal species. Analysis by longitudinal groups revealed that the lowest proportion of polyploids was noted among species found only in Eurasia and absent in North America (61%), and it was the highest among pluriregional species (96%). The species of the families Cyperaceae, Lemnaceae, Ranunculaceae and Poaceae are characterized by a high level of variability in the number of chromosomes. The greatest variety of chromosome numbers is observed in the polymorphic species Caltha palustris s. l., Agrostis stolonifera, Dupontia fisheri s. l., Phragmites australis, in all species of the genus Eleocharis, and in Nymphaea tetragona, Acorus calamus, Calla palustris. The isolated cases of a high level of ploidy were found in the extreme northeast, at the northern borders of ranges, in 3 species - Hippuris vulgaris, Arctophila fulva and Beckmannia syzigachne. Only diploids are known in the families Equisetaceae, Typhaceae, Zosteraceae from the flora of North East Asia. We revealed the existence of several chromosomal races in Ranunculus gmelinii and Caltha palustris (Ranunculaceae) in the Magadan region; the distribution of chromosomal races is partly related to geographic location and partly to plant habitats. Rare karyotypes in these species are observed in aquatic forms with mainly vegetative reproduction, growing in non-freezing watercourses.

Micropropagation of Hibiscus moscheutos L. \u2018Luna White\u2019: effect of growth regulators and explants on nuclear DNA content and ploidy stability of regenerants

Hibiscus moscheutos L., also known as hardy hibiscus, is valued for its medicinal and ornamental attributes. It is usually propagated via seeds or cuttings. The purpose of this investigation was to develop a dependable micropropagation for H. moscheutos ‘Luna White’. To that end, the effect of four explant types (leaf, root, node, shoot tip) and two growth regulators 6-benzylaminopurine (BA) and meta-Topolin (mT) (6-(3-hydroxybenzylamino) purine) on in vitro growth of H. moscheutos was investigated. Genetic stability of the in vitro grown plants was assessed using flow cytometry, and chromosome count was investigated. No shoots were obtained from leaf or root explants. An efficient protocol for micropropagation of H. moscheutos using two explant types, 2-node and shoot tip explants, and two cytokinins (BA and mT) capable of producing true-to-type regenerants was established. Both BA and mT can be used at 2 μM or 4 μM using either 2-node or shoot tip explants. No significant difference was found between the nuclear DNA contents of seed-derived and in vitro grown plants (P < 0.05). The mean 2C DNA and monoploid 1Cx-values of seed-derived plants were 3.25 ± 0.08 pg and 1.62 ± 0.04 pg, respectively, compared with 3.26 ± 0.06 pg and 1.63 ± 0.02 pg, respectively, for in vitro grown plants. The chromosome number of both seed-derived plants and regenerants was determined to be 2n = 2x = 38. The mature regenerants obtained were fertile and phenotypically similar to seed-derived plants.

Gene count from target sequence capture places three whole genome duplication events in Hibiscus L. (Malvaceae)

BackgroundThe great diversity in plant genome size and chromosome number is partly due to polyploidization (i.e. genome doubling events). The differences in genome size and chromosome number among diploid plant species can be a window into the intriguing phenomenon of past genome doubling that may be obscured through time by the process of diploidization. The genus Hibiscus L. (Malvaceae) has a wide diversity of chromosome numbers and a complex genomic history. Hibiscus is ideal for exploring past genomic events because although two ancient genome duplication events have been identified, more are likely to be found due to its diversity of chromosome numbers. To reappraise the history of whole-genome duplication events in Hibiscus, we tested three alternative scenarios describing different polyploidization events.ResultsUsing target sequence capture, we designed a new probe set for Hibiscus and generated 87 orthologous genes from four diploid species. We detected paralogues in > 54% putative single-copy genes. 34 of these genes were selected for testing three different genome duplication scenarios using gene counting. All species of Hibiscus sampled shared one genome duplication with H. syriacus, and one whole genome duplication occurred along the branch leading to H. syriacus.ConclusionsHere, we corroborated the independent genome doubling previously found in the lineage leading to H. syriacus and a shared genome doubling of this lineage and the remainder of Hibiscus. Additionally, we found a previously undiscovered genome duplication shared by the /Pavonia and /Malvaviscus clades (both nested within Hibiscus) with the occurrences of two copies in what were otherwise single-copy genes. Our results highlight the complexity of genomic diversity in some plant groups, which makes orthology assessment and accurate phylogenomic inference difficult.

Chromosome numbers of 36 vascular plants in South Korea

Variation or constancy in the chromosome number, within taxa of different categories, proves to be important characters for taxonomic groupings. To expand the current knowledge on somatic chromosome numbers of South Korean vascular plants, chromosome counts were made for 36 species (27 genera of 16 families). New chromosome numbers compared to previous studies were counted in Sedum oryzifolium, Cinnamomum japonicum, Lysimachia clethroides, and Chrysosplenium flagelliferum, respectively. Among studied species, the diploids prevail. In addition, Eupatorium lindleyanum, L. clethroides, and Lysimachia mauritiana showed polyploidy.

In vitro androgenesis: spontaneous vs. artificial genome doubling and characterization of regenerants.

Androgenesis has become the most frequently chosen method of doubled haploid (DH) production in major crops. Theoretically, plantlets derived from in vitro cultured microspore encompass halfof the normal chromosome number of donor plants and thus, considered to be haploid. However, depending on species/genotype and the method of haploid production, either via anther or isolated microspore culture, different ratios of spontaneous DHs and diploid (2n) or even polyploid plants originating from somatic tissues or unreduced gametes may also arise in the cultures. Adopting the method of haploid identification, anti-microtubular agent for restoring fertility, and discriminating spontaneous DHs from undesired heterozygote plants will substantially affect the success of androgenesis in breeding programs. The recent advances in the last 2decades have made it possible to characterize the in vitro regenerants efficiently either prior to genome duplication or using in breeding programs. The herein described approachesand antimicotubular agents are, therefore, expected to improve the efficiency of DH-based breeding pipeline through the in vitro androgenesis.

Fern Genomics: Unfurling the Mystery of Plant Chromosome Numbers

Fern Genomics: Unfurling the Mystery of Plant Chromosome Numbers

Analysis of Ploidy Levels of Korean Wild Asteraceae Species Using Chromosome Counting

Because of their attractive and colorful flowers, many species from the genus Aster serve as garden plants. Chrysanthemum owes its popularity to its ornamental and medicinal herb value. It can be used as a cut flower, potted plant, vegetable, and herbal tea. Plant breeders have attempted to identify the available species and produce new cultivars to improve the quality of chrysanthemum for commercial purposes. The use of cytogenetic studies has paved the way for identifying compatibility, ancestry, and other useful information for this undertaking. Thus, an investigation was conducted into the chromosome numbers of 23 wild Asteraceae species in Republic of Korea to determine their genetic characteristics and variations. The somatic chromosome spread has been used for chromosome counting. The results revealed that Asteraceae species have a chromosome range from 18 (diploid) to 54 (hexaploid). These findings provide primary and important information on the chromosome numbers in chrysanthemum plants that can be used to select the right variety for cultivation.

In vitro chromosome doubling of African daisy, Gerbera jamesonii Bolus cv. Mini Red

A protocol for in vitro polyploidy induction was developed in Mini Red cultivar of African daisy (Gerbera jamesonii). Various concentrations of colchicine (0, 0.05, 0.1, 0.2, 0.5 and 1%) were applied with different exposure durations (2, 4 and 8 h) on 2 weeks old explants originated from in vitro induced Gerbera shoots. Murashige and Skoog (MS) medium supplemented with 8.8 μM 6-benzyladenine (BAP) plus 11.4 μM indole-3-acetic acid (IAA) were used for proliferation of the explants. Root induction occurred when proliferated colchicine-treated shoots transferred to the half strength MS medium supplemented with 3.99 μM IAA. The results of analysis based on the comparison of means revealed that increasing concentrations of colchicine led to significant reduction in survival rate of Gerbera in longer exposure durations; however we achieved the highest survival rate with polyploidy induction by using 0.1% (w/v) colchicine for 8 h. We obtained the highest percentage of tetraploid plants (53.3%) by applying 0.2% colchicine for 2 h. Direct chromosome counting method verified the duplicated chromosome number in colchicine-induced tetraploid plants (2n = 4x = 48) in comparison with intact diploid plants of Gerbera (2n = 2x = 24). Colchicine-induced tetraploid plants of Gerbera represented reduced stomata density with wider size than their diploid relatives. In vitro tetraploidy induction led to larger flower size, longer stalks, broader leaf length and width and lower shoots in Mini Red cultivar of Gerbera. The optimized polyploidy induction protocol has high commercial value and can be also applicable for in vitro micropropagation of Gerbera.

Epigenetic consequences of interploidal hybridisation in synthetic and natural interspecific potato hybrids.

Interploidal hybridisation can generate changes in plant chromosome numbers, which might exert effects additional to the expected due to genome merger per se (that is genetic, epigenetic and phenotypic novelties). Wild potatoes are suitable to address this question in an evolutionary context. To this end, we performed genetic (AFLP and single sequence repeart (SSR)), epigenetic (MSAP), and cytological comparisons in: (1) natural populations of the diploid cytotype of the hybrid taxonomic species Solanum×rechei (2n=2×, 3×) and its parental species, the triploid cytotype of Solanum microdontum (2n=2×, 3×) and Solanum kurtzianum (2n=2×); and (2) newly synthesised intraploidal (2××2×) and interploidal (3××2×) S.microdontum×S.kurtzianum hybrids. Aneuploidy was detected in S.×rechei and the synthetic interploidal progeny; this phenomenon might have originated the significantly higher number of methylation changes observed in the interploidal vs the intraploidal hybrids. The wide epigenetic variability induced by interploidal hybridisation is consistent with the novel epigenetic pattern established in S.×rechei compared to its parental species in nature. These results suggest that aneuploid potato lineages can persist throughout the short term, and possibly medium term, and that differences in parental ploidy resulting in aneuploidy are an additional source of epigenetic variation.

Chromosome number and karyomorphologic studies of endemic Astragalus victoriae Podlech - Kirchhoff

This paper is the first report known concerning with chromosome number and morphology of Astragalus victoriae Podlech & Kirchhoff in Turkey. Karyomorphological analyses includes the chromosome length, centromer position, the arms rates (short/long) and asymmetry indices. In the analyses, the chromosome number of A. victoriae was determined as 2n = 2x = 16 and this data was consistent with the suggested chromosomal counts in Index to Plant Chromosome Numbers (IPCN) for the genus. The karyotype of A. victoriae consists of metacentric and submetacentric chromosomes and the species is seen fairly different from in points of chromosome lengths (CVCL: 30.774). The chromosome formula has been determined as 2sm+14m and the species consists of symmetric chromosomes (AI: 2.958, CI: 46).

Chromosome numbers of some Asteraceae species from Universitas Indonesia Campus, Depok, Indonesia

Salamah A, Oktarina R, Ambarwati EA, Putri DF, Dwiranti A, Andayani N. 2018. Chromosome numbers of some Asteraceae species from Universitas Indonesia Campus, Depok, Indonesia. Biodiversitas 19: 2079-2087. Asteraceae is the largest plant family, comprising of more than 1,600 genera and 23,000 species with a worldwide distribution. Many species of Asteraceae are found to be very significantly abundant in a range of habitats and are used as sources of medicines, food, forage, and other useful products. Many cytological studies have been carried out on Asteraceae. However, information about the chromosome numbers of Asteraceae in Indonesia is still very limited. In this study, the chromosome numbers of 15 species of Asteraceae found around the Universitas Indonesia campus were counted. For chromosomal preparations, the root/shoot tips were pretreated with 2 mM 8-hydroxyquinoline, stained with aceto-orcein, prepared using the squash method, and then observed with a microscope. Of the 15 species, 12 showed variation in chromosome numbers: Cosmos caudatus, Elephantopus scaber, Tridax procumbens, Mikania micrantha, Sphagneticola trilobata, Ageratum conyzoides, Cyanthillium cinereum, Chromolaena odorata, Synedrella nodiflora, Youngia japonica, Eclipta prostrata, and Porophyllum ruderale. The other three species showed no variation in chromosome number: Emilia sonchifolia (2n=10), Sonchus arvensis (2n=18), and Cosmos sulphureus (2n=24). We also found new variations in chromosome numbers that have not yet been listed in the Index to Plant Chromosome Numbers (IPCN).

Efficient Parthenogenesis Induction and In Vitro Haploid Plant Regeneration in Cucumber (Cucumis sativus L.) Using Putrescine, Spermidine, and Cycocel

In this study, the effect of spraying mother plants with various levels of putrescine, spermidine, and cycocel (each at 0, 50, 500, and 5000 mg/l) were assessed on the frequency of haploid embryos produced from unfertilized ovaries and subsequent regeneration of derived embryos. Significantly higher haploid embryos were obtained when mother plants were sprayed with putrescine at 500 mg/l (5.2 embryos/fruit), spermidine at 50 mg/l (4.8 embryos/fruit), and cycocel at 50 mg/l (5.2 embryos/fruit) as compared to the control (without spraying, 3.2 embryos/fruit). However, embryogenesis induction was decreased drastically as the concentration of all the three compounds tested was increased and the lowest haploid embryos were observed when 5000 mg/l of spermidine (0.4 embryos/fruit) or cycocel (2.0 embryos/fruit) were applied. Only spermidine at 50 mg/l led to 100% regeneration into fully developed plantlets. The seed setting and size of fruits were also affected by polyamines and cycocel applications. Ploidy analysis using a flow cytometer indicated that all regenerated plantlets contain the gametic chromosome number (n = x = 7) of parental plants and the results of chromosome counting also confirmed the haploid nature of regenerated plantlets. It can be concluded that the induction of haploid embryogenesis from unfertilized ovaries after pollination with irradiated pollen and subsequent conversion of derived embryos into the plantlets could be improved in Cucumis sativus L. by applying appropriate levels of putrescine, spermidine, and cycocel.

Cytotypes ofSprekelia formosissima(Amaryllidaceae) collected in three localities of the state of Jalisco, Mexico

Sprekelia formosissima (L.) Herbert is a bulbous ornamental species of the Amaryllidaceae family, distributed from northern Mexico to Guatemala. Different reports on cytogenetic research on this species show differences in chromosome numbers (2n = 60, 120, 150, 180) with a basic number of x = 30. Since the chromosome number of plants can provide useful information for various fields of research including karyotaxonomy, genetics, and cytogenetics, it is important to determine the chromosome number for this species. Bulbs of S. formosissima were collected in three different locations in the state of Jalisco, Mexico. Meristematic root cells were analyzed cytogenetically using a modified steam-drop method. The three populations showed different chromosome numbers and ploidy levels, 2n = 2x = 60, 2n = 4x = 120, and 2n = 5x = 150. The ploidy level was compared with morphological traits showing higher values related to higher ploidy levels. The populations analyzed correspond to new polyploid cytotypes of S. formosissima.

The Value of Agricultural Voucher Specimens

Voucher specimens are the ultimate raw data of biodiversity studies because they document the interpretation of the names used in papers and reports resulting from such studies. The value of voucher specimens is increased by making their records web-accessible but they can be further enhanced by linking them to other online resources, particularly if the links are birectional. In this presentation, we discuss the potential benefits of such links for a group of agricultural significance, the Triticeae, a tribe of grasses that includes wheat, barley and rye among its 300+ species. The late Dr. D.R. Dewey conducted extensive cytogenetic studies in the tribe and deposited voucher specimens in the herbarium of Utah State University. Some of the voucher specimens were collected in the region but the majority were grown from germplasm accessions obtained from GRIN, the United States Department of Agriculture's Germplasm Resources Information Network. The specimen labels of the GRIN vouchers hold minimal information but one item that is present is the “PI Number” or GRIN identifier. Linking the GRIN vouchers to data in the GRIN database gives access to the original collection information, which is often complete enough to permit georeferencing the specimen, thereby enabling it and any derived information to be associated with the environmental parameters at the point of collection. The links could also be used to disseminate changes in identification of the voucher specimen to genebanks with duplicates of the original accession. The PI numbers also link the specimens to trait data deposited in the world’s genebank system and to publications in which the accession was cited, regardless of whether they relate to the original intent of the seed collectors. The impediment is that few collection databases are designed for effective capture of genebank identifiers. Another problem, from a taxonomic perspective, is that such stored trait information is of agricultural but not taxonomic value. Thus, one challenge is to modify specimen database systems so that they can effectively store taxonomically useful data; the other is to persuade those working on a taxonomic group to identify, score, and share data about core taxonomically useful characters for the group. Such “databases” currently exist, if at all, as a spreadsheet on an individual’s computer and may represent hours of labor measuring multiple features of individual specimens. Another potential linkage for many herbarium specimens is the Index of Plant Chromosome Numbers (IPCN). Again, one problem is providing easy access to the linking fields in both IPCN and the collection database; another is the lack of funding for maintaining IPCN. Linking specimens to sequence data is, by comparison, relatively simple but it would be useful for herbarium and genebank managers to know when the specimens/accessions they curate or have duplicates of have been used in a molecular study. Moreover, GenBank needs to have a mechanism for reporting that the identification of a voucher specimen has been changed. Our interest in these questions arises from a decision by The International Triticeae Consortium, a group that shares a common interest in members of the Triticeae, to pursue development of a web site that would provide access to data about the tribe’s members. Because of the economic importance of wheat, barley, and rye, the tribe is studied in almost every country. It is also the subject of significant taxonomic disagreement, an aspect that can present an impediment to those working with its members. Although the presentation will focus on the Triticeae, the approach and principles involved would apply to any taxonomic group.

An assessment of the genetic integrity of micropropagated raspberry and blackberry plants

In vitro clonal propagation of small fruit species has been one of the most broadly exploited approaches in biotechnology. However, the most critical aspect of this propagation technology has been the maintenance of genetic fidelity of tissue culture-raised plants. In the present study, three techniques were deployed in the assessment of genetic fidelity of micropropagated plants (TC plants) of blackberry cultivar ‘Čačanska Bestrna’ and raspberry cultivar ‘Meeker’ in the second year after planting in the open field, in comparison to plants originating from the standard planting material (ST plants). Flow cytometry analysis deployed to estimate the DNA ploidy level and relative nuclear DNA content in TC and ST plants revealed no significant differences in nuclear DNA content between plants of different origin. Chromosome counting in root/shoot tip meristems also showed a normal tetraploid chromosome number (2n=4x=28) in TC blackberry plants and a normal diploid chromosome number (2n=2x=14) in TC raspberry plants. Polyacrylamide gel electrophoresis of peroxidase (POX) extracted from the leaf tissue revealed no differences in POX profiles between TC and ST plants either. The results obtained in this study verify the suitability of micropropagation by axillary branching for commercial exploitation in blackberry and raspberry.

Effect of colchicine-induced polyploidy on morphological characteristics and essential oil composition of ajowan (Trachyspermum ammi L.)

Polyploidy is an amazing evolutionary event that can be used in plant breeding to improve plant material. The present study was conducted to assess the effect of in vitro-induced polyploidy on different properties of Ajowan medicinal plant. Five different concentrations of colchicine, including 0.025, 0.05, 0.1, 0.2, and 0.5% (w/v), were applied to germinating seeds of ajowan in six different durations of exposure, including 6, 12, 24, 36, and 48 h. Chromosome counting showed successful duplication of chromosome number in tetraploid plants (2n = 4x = 36) in contrast with intact diploid plants (2n = 2x = 18). DNA content duplication in induced tetraploid plants was proved through flow cytometry analysis. The highest tetraploidy induction was achieved by applying 0.05% (w/v) colchicine for 24 h with 11.53% efficiency. The tetraploid plants achieved were larger than their diploid intact plants for plant height, leaf length, stem diameter, inflorescence length, peduncle length, and seed length characteristics. The length and width of stomata were increased in induced tetraploid plants, whereas stomata density was decreased, in contrast with initial diploid plants. Gas chromatography mass spectrometry (GC/MS) analysis showed significant increases in thymol content in essential oil of tetraploid plants (69.2%) in contrast with those of diploid plants (49.67%).

Chromosome numbers of 50 vascular plants in South Korea

Variation or constancy in the chromosome number within taxa of different categories have been proven to be important characters for taxonomic groupings. In order to expand the current knowledge on somatic chromosome numbers of South Korean vascular plants, chromosome counts were made for 50 species (38 genera of 17 families). The first chromosome information for Glaux maritima var. obtusifolia Fernald, Hemerocallis hakuunensis Nakai, Hylotelephium verticillatum (L.) H. Ohba, Orostachys iwarenge f. magnus Y.N. Lee, and Teucrium viscidum var. miquelianum (Maxim.) Hara is presented. New chromosome numbers compared with previous studies are also counted in Aconitum pseudolaeve Nakai, Securinega suffruticosa (Pall.) Rehder, and Tricyrtis macropoda Miq., respectively. In addition, Eupatorium japonicum Thunb. is proven to show polyploidy with tetra- and pentaploid. Among studied species, the diploids (66%) and tetraploids (24%) prevail.

Induced Homoeologous Pairing for Transfer of Useful Variability for High Grain Fe and Zn from Aegilops kotschyi into Wheat

Biofortification of bread wheat by the transfer of useful variability of high grain Fe and Zn from Aegilops kotschyi through induced homoeologous pairing is the most feasible approach to alleviate micronutrient malnutrition worldwide. Deficiency of chromosome 5B in interspecific hybrids allows homoeologous pairing and recombination of chromosomes of wheat with those of the related species. The interspecific hybrid plants without 5B chromosome showed much higher chromosome pairing than did the plants with 5B. The F1 plants without 5B chromosome were selected and repeatedly backcrossed with wheat cultivar PBW343. The chromosome number of BC2F1 plants ranged from 43 to 60 with several univalents and multivalents. Molecular markers and GISH analysis confirmed the introgression of U/S chromosomes of Ae. kotschyi and their fragments in wheat. The BC2F2 plants showed up to 125 % increase in Fe and 158 % increase in Zn compared to PBW343 with Lr24 and Yr36. Induced homoeologous pairing in the absence of 5B was found to be an effective approach for transfer of useful variability for enhanced grain Fe and Zn content for biofortification of wheat for high grain micronutrient content.

Chromosome Observation of Rice Root Tip and Effect of Callus Colour Variation and Texture in Different Colchicine Concentrations on the Induction of Rice Polyploids

The abiotic stresses course major environmental factors that determine the most serious yield reduction in rice (Oryza sativa L.). The abiotic stresses tolerant ability can be improved by changing typical chromosome number of plants. The objectives of the studies were to evaluate the performance of callus of rice cultivars (Suwadel and Sulaai) for different Colchicine concentrations to produce polyploidy for enhance tolerant characteristics to drought and salinity stresses. Surface sterilized seeds were introduced to Murashige and Skoog (MS) basal medium with hormone 2mgL-1 2,4-D (2, 4-dichlorophenoxyacetic acid) and 0.1 mgL-1 BAP (6- benzylamino purine) for callus induction. Callus of 0.5cm2 from rice cultivars introduced to different Colchicine concentrations (0, 30, 60, 90 and 120 mgL-1) and different time durations (12, 24 and 78 hours). Treated callus were introduced to shoot regeneration on MS medium with 0.1mgL-1 IAA (Indole acetic acid) and 2mgL-1 BAP. Colour, texture and regeneration ability of callus were recorded after one month. Completely Randomized Design (CRD) with five replicates was used for study. Statistical analysis was performed with Duncan's multiple range tests using SAS software (version 9.1.3). Results showed that callus treated from Colchicine 30, 60, 90 and 120 mgL-1 in 12 hours and, 30, 60, 90 mgL-1 in 24 hours have potential to survive. Increasing Colchicine concentration and time duration showed that regeneration ability of callus reduced in selected rice varieties.

A comparison of plant chromosome number variation among Corsica, Sardinia and Sicily, the three largest Mediterranean islands

Chromosome counts of the vascular floras of Corsica, Sardinia, and Sicily were compared quantitatively, based on data stored in the online database “Chrobase.it”, and analysed to determine any trend associated to the latitudinal range. Mean chromosome number (CN) ± SD, frequency of B-chromosomes occurrence (fB), frequency of odd CN, and ICNH (Index of Chromosome Number Heterogeneity) were calculated for each island’s flora. The relative frequency of putative even ploidy levels was also calculated for the most frequent base numbers (x = 7, 8, 9) as the percentage of cytotype frequency value relative to the total sum of cytotypes. Our results show that ICNH and mean CN are lower in Sicily and higher in Sardinia and Corsica; furthermore, the relative frequencies of cytotypes of putative even polyploid series decrease with increasing ploidy levels, which can be modelled by an exponential decay of the general form f(x) = e(ax+b), with different parameters in the different islands. Such results are in agreement...